The performance of a mechanical seal, which is an example of a sliding component, is evaluated based on the leakage rate, wear rate, and torque. Mechanical seals of prior arts have achieved greater performance in the form of low leakage, long life, and low torque by optimizing their sealing material and roughness of seal area. In recent years, however, the ever-growing awareness of environmental issues in the market has created a demand for mechanical seals offering even higher performance and a consequent need to develop technologies that go beyond the scope of prior arts.
Under the circumstances, the inventor of the present invention has shown that, in the case of mechanical seals for water pumps used to cool water-cooled engines, for example, additives for LLC (long-life coolant), which is a type of antifreeze agent, such as silicate and phosphate (hereinafter referred to as “causative substances for deposits”), may accumulate on the sealing face over time to generate deposits that can cause mechanical sealing properties to drop. This generation of deposits is a phenomenon that also occurs with mechanical seals for equipment handling chemicals and oils.
Known among conventional mechanical seals are those having fluid introduction grooves, which are formed on their sealing face in order to form a fluid layer and thereby prevent wear and burn damage that would otherwise be caused by generation of frictional heat on the sealing face (refer to Patent Literatures 1, 2 and 3, for example), but the present reality is that none of them provides a measure to reduce leakage or wear, not to mention preventing generation of deposits on the sealing face.